Monday, August 12, 2013

New Prototype Robot Developed for Pediatric Shoulder and Hip Arthrography

American children ages 5-14 experience an average of one or more sports-related injuries per year, often involving internal derangement of shoulders, hips, wrists and other joints [1].  In such cases, arthrography can assess the condition of a joint, using imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI). The modality of choice to diagnose soft-tissue injuries in children is magnetic resonance (MR) arthrography since it involves no radiation and provides higher soft-tissue contrast than CT imaging.

However, currently MR arthrography requires two separate stages: an intra-articular contrast injection guided by fluoroscopy or ultrasound, followed by an MRI. In typical interventions, the physician guides a needle using cross-sectional images, often requiring multiple passes to reach the target. In MRI-guided interventions, patient access can be difficult, especially in closed bore scanners. The inability to leverage the imaging capabilities of the MRI itself to guide the needle and the manual nature of needle placement lead to increased cost, anxiety and in some cases prolonged sedation time - especially for the youngest and most anxious patients.

To address these limitations, researchers and engineers in the Sheikh Zayed Institute are developing a novel, patient-mounted CT and MRI robotic system to provide better targeting, improve the clinical workflow and allow better access with the MRI scanner bore.

Developing equipment compatible with a high magnetic field is the major challenge for a robotic system in MRI-guided interventions, so as a first step the Sheikh Zayed team has developed a CT-compatible prototype for shoulder and hip arthrography for pediatric use. This small and lightweight robot uses adhesive tape and straps for stable attachment to the patient's body. During procedures, major portions of the robot can be covered with sterile plastic sheets, and the remaining parts can manufactured to be disposable or to be sterilized for re-use.

Solidworks 3D model of the final design.

Final design.

The robot will connect to a computer through a Galil motor controller. Software—a dialog-based MFC application in Visual C++ on the Windows operating system—will convert input from the user interface devices into control signals to drive the robotic mechanism.
The prototype has three degrees of freedom for needle guidance and insertion. Two possible approaches will be tested for guiding the robot: 1) the physician controls the robot from the MRI control room with a joystick; or 2) the robot pre-aligns its trajectory to a commanded path on the MRI images and an indication from the physician of the target, and the physician manually drives the needle to the target while the robot maintains the trajectory.

With the initial design and prototype completed, the next step is to demonstrate the workflow and targeting capability in the CT environment. Ultimately, the team plans to develop an MRI-compatible robot capable of automatically driving a needle and injecting contrast material during a real-time MRI sequence to observe joint function and make an accurate diagnosis, shortening and streamlining procedure times for children.

[1] Shital Parikh, “The Trend of Pediatric Sports and Recreational Injuries in the U.S. in the Last Decade”, American Academy of Orthopaedic Surgeons's (AAOS) Anual meeting, 2013.

Posted on behalf of Kevin Cleary, PhD

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